We report a new class of high k dielectrics based on ternary amorphous metal oxide, Bi1-x-yTixSiyOz (BTSO, x = 0.4, y = 0.2). BTSO films grown by atomic layer deposition (ALD) have a dielectric constant of 55-64, which is the highest value reported among amorphous dielectric films. Leakage current density of the films is on the order of 10(-8) A/cm(2) at 1 V with dielectric breakdown strength of 0.6-1.6 MV/cm. Thickness and compositional uniformities on hole structures with a high aspect ratio (7) are also investigated with Bi2Ti2O7 films without Si, of which conformality is excellent with respect to both thickness and composition. (C) 2004 The Electrochemical Society.